Rails, being on

An uncomplimentary description of a game that is excessively linear, preventing the player from doing things in an order not anticipated by the author. The opposite would be a game in which the player is allowed, for instance, to tackle any one of a half-dozen puzzles at a given time. Preferably the order in which the puzzles were solved would result in different plot twists, a congenial counterpart to irrecoverability in a game. (See cruelty scale.)